Packet switched networks generally are based on shared bandwidth topology. In this topology, each node has unlimited and uncontrolled access to network resources. A commonly used network access system, known as statistical multiplexing, transmits data simultaneously from any number of input devices attached to the network, and offers maximum utilization of the network's available bandwidth by assigning to each device unrestricted access to the network. However, with this kind of multiplexing, several inherent problems arise:                Network behavior is erratic and unpredictable due, in part, to collisions between data packets that different nodes are attempting to transmit at the same time.        Network resources are unfairly distributed, with ingress nodes which are closer to certain egress nodes getting much more bandwidth than ingress nodes which are remote from those egress nodes.        Traffic parameters, such as delay (the time lag between the departure of a signal from the source and the arrival of the signal at the destination) and jitter (the variance from the average delay), cannot be assured.        It is impossible to guarantee quality of service, in terms of assured bandwidth, bound delay and jitter, and packet loss, to differentiated customers or services, as defined in Service Level Agreements (SLAs).        
Conventional solutions and practices for data networks involve adding complex management protocols, which generally are based on packet-by-packet traffic handling and heavy error correction and data integrity algorithms. These solutions, however, are based on local (per hop) calculations and information, and are prone to errors due to global dynamic changes, e.g., a sudden rise in network resource use in one node that causes the network to be congested for the time (typically, a few seconds) it takes for the resource management protocols to stabilize the network. With conventional dynamic networks, only over-engineering of the network can assure that the peak network use is adequately met without disturbing guaranteed traffic. This results in under-utilization of network resources at other times.
One example of admission control of traffic based on per hop statistics is shown in US patent application 2004/0128384 to Rolia, et al. This application relates to admission control of applications in resource utility environments. The method of admission control includes determining the application's statistical demand profile for resources required by the application seeking admission; determining an assurance level of the resource utility; and admitting the application based on the statistical demand profile of the application, the assurance level of the resource utility, and statistical demand profiles of one or more applications currently hosted by the resource utility. This method utilizes no prior knowledge or rules of the applications resource usage, but only a computed statistical demand profile. Thus, it is limited in its efficiency as it has no knowledge of the state of the overall system.
Another example of a prior art solution is disclosed in U.S. Pat. No. 6,771,598 to Andrews. This patent describes a method for determining the admissibility of an offered session of traffic of a specified class to a server in a packetized communication network. The method involves defining an operating point for the server which represents the number of sessions of each respective class currently offered or currently being served, and determining whether this defined operating point falls within an admissible region. The admissible region consists of operating points for which the probability of violating a delay bound for any packet is below a threshold value. This method performs admission control based on calculation of each server's abilities based on some a priori knowledge of its behavior, and not based on actual traffic behavior throughout the network.
A further example is shown in U.S. Pat. No. 6,791,941 to Dziong, et al. This patent relates to tuning for connection admission control (CAC) algorithms in broadband ATM networks, which is accomplished using an overbooking technique based on aggregate effective bandwidth as an approximation to required bandwidth for given levels and classes of network traffic. This patent is based on a trial-and-error method for determining optimized rate control of each local traffic stream, and has no knowledge of the state of the network.
Furthermore, packet switched networks are (at the data link layer), connectionless, shared bandwidth networks which interconnect nodes in an arbitrary way. In order to establish a connection between the nodes for transmission of data, a routing mechanism is required. Current routing protocols are designed to cope with dynamic and unpredictable volumes of data transfer through networks that are characterized by dynamic topology composed of many nodes that communicate with each other in an arbitrary and random way. These networks are typically enterprise networks or the Internet. To address these problems, routing protocols are adapted to cause each router to continually learn the network topology and continually collect information about traffic status throughout the network, take note of the volume of data being routed through each node, calculate optimized routes for each possible connection and update routing tables at each routing node. Thus, each router computes, independently of the other routers, its own routing table, which is the basis for its forwarding decisions. The information is based on local (adjacent hops) information, as the individual routers have no knowledge of the overall traffic load or performance in the network. Therefore, it is sub-optimal, on one hand, as it does not take into account the other nodes in the network, while heavily burdening the routing node, on the other hand.
US Patent Application 20020150041 to Reinshmidt, et al. describes a method and system for improving the quality of service for transportation of selected data packets over an IP-based data network, such as the Internet. The method utilizes servers in the customer's environment, each of which serves as a source node or destination node. Preferably, for each link, several alternative paths are pre-selected. The servers contain unique software which allows the servers to exchange test packets between them to monitor and analyze the transportation parameters of each alternative path. When an optimal path is identified, the server modifies the header of the data packet, thereby causing the data packet to be forwarded to the destination node via the selected optimal path(s).
In this method, the paths are monitored between pairs of nodes and not globally. Furthermore, there is no provision for admission control of data to the network, so collisions are likely.
US Patent Application 2002/0174246 to Tanay, et al. describes a centralized system that computes routing tables for routers in an IP protocol network, and removes the task of computing routes from the individual routers. This system includes a network traffic statistics gathering system, a matrix formation and optimization system for classifying the traffic into classes and computing optimized routes for every traffic class according to the traffic statistics, and a distribution system for distributing routing tables, including information concerning the optimized routes, to the individual routers. This system, which is limited in use to an IP networking system, must learn the new topology state of the network whenever there is a change of any sort. Since these computations are required continually, the network is burdened with large quantities of computations, and automatically “updates” routing tables, substantially in real time, even if there are no changes, thereby slowing down data transfer in the network as a whole. In addition, this system has no provision for admission control of data to the network, leading to inefficient transfer of data traffic.
Carrier transport networks, for example, metro area networks, which are used to transport core data traffic, do not resemble enterprise networks or the global Internet. Rather, the carrier transport network is a conventional telephony network, and is characterized by different attributes:                The logical network's topology is usually mesh based.        The physical network is usually ring based.        The network consists of well-defined autonomous routing domains.        Each node is connected to specific node(s) within each domain.        Available routes are known and limited in number, and are static until the topography of the network changes.        All traffic of one service from one node within each routing domain is destined to a relatively small, finite and constant group of nodes.        
These networks suffer from the disadvantage that they are inefficient. In order to ensure that all required traffic is transported over the network within a reasonable time, the network is often under-utilized. Thus, empty frames are often sent over the network.
Furthermore, it will be appreciated that the complex routing protocols described above, designed for generalized global and dynamic topology networks, which require constant updating of routing tables in accordance with the actual state of the various nodes in the network, are not suitable for establishing routes in the routing domain of a carrier network, such as a metro network. This is because they are too complex, and they are not resource efficient or cost efficient.
None of these prior art methods provides Quality of Service for data packets in metro and sub-networks of carrier networks, and so forth, which is close to optimal. Accordingly, there is a long felt need for a system for transmitting data packets over a network which provides QOS which is close to optimal and can be adjusted when required, having the stability and reliability of conventional carrier networks as well as the flexibility and adaptability of conventional global networks, and it would be very desirable to have such a system which provides more balanced utilization of network resources.